Tanks on Carpet

How long is the tank going to be there?

The carpet under the stand is not going to get walked on, thus will be in better shape in a couple years than the main area of the room. Once the weight is removed, it'll just take a little time for the fluff to get back into the carpet. The biggest problem will be food and water spills staining the carpet near the stand. So, perhaps put a throw rug in front of it to catch spills and you'll be good to go.

tank will be there for a year or 2

I was going to put down some carpet around the tank to prevent what you are talking about (I trashed a floor in an apartment once from a water spill.)

I put down clear vinyl runners under my tanks. You can purchase them by the foot at Lowe's or Home Depot.